Heater



FIG. 1 is a front left perspective view of a heater showing our new design;

FIG. 2 is a rear perspective view;

FIG. 3 is a front elevation view;

FIG. 4 is a right elevation view;

FIG. 5 is a left elevation view;

FIG. 6 is a top plan view; and,

FIG. 7 is a rear elevation view.

In the drawings, the broken lines depict unclaimed subject matter only and form no part of the claimed design. 

The ornamental design for a heater, as shown and described. 